Brucella suppress STING expression via miR-24 to enhance infection

PLoS Pathog. 2020 Oct 27;16(10):e1009020. doi: 10.1371/journal.ppat.1009020. eCollection 2020 Oct.

Abstract

Brucellosis, caused by a number of Brucella species, remains the most prevalent zoonotic disease worldwide. Brucella establish chronic infections within host macrophages despite triggering cytosolic innate immune sensors, including Stimulator of Interferon Genes (STING), which potentially limit infection. In this study, STING was required for control of chronic Brucella infection in vivo. However, early during infection, Brucella down-regulated STING mRNA and protein. Down-regulation occurred post-transcriptionally, required live bacteria, the Brucella type IV secretion system, and was independent of host IRE1-RNase activity. STING suppression occurred in MyD88-/- macrophages and was not induced by Toll-like receptor agonists or purified Brucella lipopolysaccharide (LPS). Rather, Brucella induced a STING-targeting microRNA, miR-24-2, in a type IV secretion system-dependent manner. Furthermore, STING downregulation was inhibited by miR-24 anti-miRs and in Mirn23a locus-deficient macrophages. Failure to suppress STING expression in Mirn23a-/- macrophages correlated with diminished Brucella replication, and was rescued by exogenous miR-24. Mirn23a-/- mice were also more resistant to splenic colonization one week post infection. Anti-miR-24 potently suppressed replication in wild type, but much less in STING-/- macrophages, suggesting most of the impact of miR-24 induction on replication occurred via STING suppression. In summary, Brucella sabotages cytosolic surveillance by miR-24-dependent suppression of STING expression; post-STING activation "damage control" via targeted STING destruction may enable establishment of chronic infection.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Brucella / genetics
  • Brucella / metabolism*
  • Brucellosis / genetics
  • Brucellosis / metabolism*
  • Female
  • Host-Pathogen Interactions / immunology
  • Macrophages / immunology
  • Male
  • Membrane Proteins / biosynthesis*
  • Membrane Proteins / genetics
  • Membrane Proteins / metabolism
  • Mice
  • Mice, Inbred C57BL
  • MicroRNAs / genetics
  • MicroRNAs / metabolism*
  • RNA, Messenger / genetics
  • Type IV Secretion Systems / genetics
  • Type IV Secretion Systems / metabolism

Substances

  • Membrane Proteins
  • MicroRNAs
  • Mirn23b microRNA, mouse
  • Mirn24 microRNA, mouse
  • RNA, Messenger
  • Sting1 protein, mouse
  • Type IV Secretion Systems